The present invention relates to a surgical bone operation instrument with a straight shaft, arranged coaxially to the longitudinal axis of the tool, which tool is provided at the side of one end of a hand piece with a working unit and at the side of the other end of the hand piece with a driving assembly.
Such a surgical bone operation instrument, which serves as a drilling or milling apparatus for dentistry work, is already known. It has a longitudinal channel, in which a small tube is extending for the guidance of a cooling means. Each time the driving means is coupled with the drill shaft, the small tube must penetrate a soft, elastic cover, which separates the channel between the drill and the shaft carrying this drill. This is a disadvantage because repeated penetration destroys the cover and it must frequently be replaced. Furthermore, the small tube must have a sharp point, which always presents a possibility of injury and therefore is undesirable; and finally there is always the danger that in penetrating the cover, the small tube will become clogged.